Whisky Magazine Issue 32
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Ian Wisniewski asks that all-important question: does the way a still is heated affect the final product?
The focus tends to fall on the influence that a still's shape, size and accessories such as boil bowls or purifiers have on the character of the new make spirit. But the rate of distillation is also crucial, and that depends on controlling the heat applied to the still, using either the indirect method (steam-heated coils within the pot) or direct-firing (burning coal or gas to heat the base of the pot).
While indirect heating is considered the easiest to control, and used by the majority of distilleries, that's only one consideration in a broader debate. Indirect heating applies a gentler, more uniform build-up of heat in the wash compared to direct-firing. Additionally, direct-firing potentially creates a more variable range of temperature on different parts of the pot's surface, which in turn can prompt different flavour effects.
Any changes to the heating method can also alter the temperature profile and so the distillation rate, which in turn affects the character of the new make spirit. Hence some distilleries agonise over changes to their heating methods, while others retain direct-firing.
Glendronach is a rarity in using coal, the most traditional method of heating stills. The type of coal, ‘washed singles,' is sourced from central Scotland and considered the most efficient for this purpose. During a distillation run, coal hoppers feed pieces of coal, around 3cm squared, into a fire box beneath the still.
The options for controlling the fire are either to increa...